The development of optical elements, including ophthalmic lenses, manufactured from plastic materials has required the development of protective coatings providing good abrasion resistance and/or scratch resistance, because organic glass is known to be more sensitive to scratching and abrasion than conventional mineral glass. Organic glass is therefore usually protected by applying a thermally or photochemically hardenable composition to the surface of the glass to produce an abrasion-resistant coating.
Another rather new and very interesting route for solving the problem of scratches and/or abrasion of organic glasses is to protect the lenses with coating layers able to repair themselves, i.e. coatings which would be able, when submitted to a simple physical treatment, to revert completely or partially to the initial non-scratched condition. Examples of such self-healing coatings have been disclosed by BAYER, PPG INDUSTRIES (Revivance®), SUPRAPOLIX BV and CRG (Veriflex® and also US 2009/062453 and WO 2009/029641). They are mainly prepared from polyurethanes, epoxies, and shape-memory (co)polymers, which show healing effects after thermal, UV or humidity treatments. These materials further contain active capsules which can crosslink with other elements once the cracks appear and open the capsules. More recently, the present inventors have found that a class of known thermocured or photocured resins obtained by thiol-ene reactions and used heretofore as UV-curable adhesives, display interesting transparency and a shape memory effect with transition temperature in the range of 45 to 65° C. These resins are the Norland Optical Adhesives (NOA) marketed by Norland Products Inc. Moreover, they found that the healing performances of these resins could be improved by incorporating conductive colloidal particles, such as Sb2O5 or SnO2, into the monomer mixture before curing.